The supply of oven-fresh bakery products to consumers has been improved by frozen dough technology; however, freeze-thaw stress decreases the activity of yeast cells. To breed better baker's yeasts for frozen dough, it is important to understand the factors affecting freeze-thaw stress tolerance in baker's yeast. We analyzed the stress response in IB1411, a spore clone from Saccharomyces cerevisiae Shirakami kodama yeast, with an exceptionally high tolerance to freeze-thaw stress. Genes encoding trehalose-6-phosphate synthase (TPS1), catalase (CTT1), and disaggregase (HSP104) were highly expressed in IB1411 cells even under conditions of non-stress. The expression of Hsp104 protein was also higher in IB1411 cells even under non-stress conditions. Deletion of HSP104 (hsp104Δ) in IB1411 cells reduced the activity of the ubiquitin-proteasome system (UPS). By monitoring the accumulation of aggregated proteins using the ΔssCPY*-GFP fusion protein under freeze-thaw stress or treatment with proteasomal inhibitor, we...

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